186 Royal Society :- — 



species. There is one coral which appears to belong to the genus 

 Errina, Gray*, of which a further diagnosis is given from the 

 type specimens by Saville Kentf, and one of the allied new 

 genus Acanthopora. The whole of the classification of the Sty- 

 lasteridae will need revision on the more certain basis of the know- 

 ledge of the structure of the soft parts. In the older regions 

 of its stem L&pidopora appears to assume the character of a 

 Stylaster. The coral for the reception of which I form the 

 new genus Polypora differs markedly from other members of the 

 family; I at first took it to be a Millepora with unusually large 

 zooids. 



The genus may be thus characterized, as far as the hard parts 

 are concerned : — 



Genus Poltpoea. 



Corallum pure white, composed of a finely reticular but com- 

 pact coenenchym. It forms single, stout, vertical stems, usually 

 compressed from before backwards, so as to be oval in transverse 

 section. The stem gives off a limited number of irregularly di- 

 chotomous branches, which are flattened like the stem from before 

 backwards, and tend to coalesce by theii* latei'al margins and as- 

 sume a flabellate form, which is sometimes somewhat curved. 

 The surface of the corallum is perfectly even and smooth, and 

 pierced by deep calicular cavities, simply circular in outline, and 

 of two kinds, large and small. The larger less numerous calicles 

 are disposed at irregular intervals over the surface ; they are veiy 

 deep, reaching nearly to the centre of the axis of the branch or 

 stem, and contain a deep-seated, very long, and slender style with 

 a brush-like tip. The more numerous smaller calicles vary in 

 size ; they are thickly disposed between the larger ones ; they have 

 no style. ISeated beneath the surface between the calicles are 

 numerous ovoid cavities, the ampuUaj, which in this genus do not 

 project ; at certain stages of development these communicate with 

 the exterior by minute irregularly shaped pores, seated ui small 

 shallow pits on the surface of the corallum. The calicles are 

 usually more abundant on one face of the corallum than on the 

 other, especially in its older basal region. 



Type of the genus Polypora dichotoma. 



Dimensions of the specimen : — Height of the corallum from 

 1| to 1 inch ; breadth of fan 6 inches ; diameter of stem from 1| 

 to 1 inch ; diameter of the mouths of the larger calicles J^ of an 

 inch. 



A further examination of the species of Stylaster obtained ofB 

 the Meangis Islands was made in connexion with that of the corals 

 referred to above. This Stylaster resembles Cryptohelia in every 

 particular, excepting that it has not the peculiar lid in front of 

 its calicles. It will have to be separated from the other Stylasters, 

 and placed in the genus Cryptohelia. 



* Proc. Zool. Soc. 1835, p. 35. t Proc. Zool. Soc. 1871, p. 282. 



